Polymethylmethacrylate resin with an impact modifier capsulated therein and a process of preparing for the same

ABSTRACT

A PMMA resin containing an impact modifier capsulated therein, said impact modifier comprising a core of a glass polymer, an intermediate layer of a rubber copolymer grafted to the core and an outer layer of a glass polymer grafted to the intermediate layer, the impact modified PMMA resin having a granular shape, the amount of the core being 5 to 20 weight %, the amount of the intermediate layer being 10 to 70 weight % and the amount of the outer layer being 25 to 85 weight %, the intermediate of the rubber copolymer being a copolymer of at least one monomer selected from the group consisting of butylacrylate and butadiene and a monomer of styrene, the outer layer of a glass polymer containing a chain transfer agent.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/KR99/00241 which has an Internationalfiling date of May 14, 1999, which designated the United States ofAmerica.

TECHNICAL FIELD

The present invention relates to a polymethylmethacrylate (herein afterreferred to as “PMMA”) resin with an impact modifier capsulated thereinwhich possesses good transparency and high impact resistance, and to aprocess of preparing the same without steps for the separate addition ofa PMMA resin and impact modifier to an extruder in order to improveproductivity.

The present invention intends to improve the conventional impactmodifier having a core-shell structure produced by two or three emulsionpolymerization steps, which includes problems that the thickness of theshell layer is increased thereby degrading the impact resistance.

Also the present invention provides a process for producing a PMMA resinwith an impact modifier capsulated therein having improved reinforcingproperties and processibility by increasing the thickness of the shelllayer without degradation of the impact resistance and having improvedproperties of transparency together with impact resistance by dispersingthe impact reinforcement agent uniformly in the products.

DESCRIPTION OF THE RELATED ART

Typically, a PMMA resin has been compounded with an impact modifier inthe production of PMMA resin products for improving impact strength andother properties. An impact modifier for the transparent acryl resinincludes a methylmethacrylate-butadiene-styrene group (hereinafterreferred to as “MBS group”), an acrylonitrile-butadiene-styrene group(hereinafter referred to as “ABS group”) and an acrylate group impactmodifier. Particularly, the impact modifier of the MBS and ABS groupsshow poor physical properties due to their low weather resistance whenused in the open air for a long period, and the producing process iscomplicated by the use of a butadiene gas. The transparency of theimpact modified PMMA is lowered because of the different refractiveindex of the components. Furthermore, the impact modifier of the ABSgroup must be used more than other kinds of the impact modifiers toobtain the same reinforcing effect.

Impact modifiers having excellent resistance against the weather andgood impact strength and may include, for example, an acrylic impactmodifier which is prepared from (meta)acrylic monomers, vinyl monomerssuch as styrene derivatives and vinyl derivatives, surfactant,initiator, crosslinking agent, and grafting agent.

The acrylic impact modifier has improved impact strength because theimpact is transferred to the acrylic rubber layer from the outer matrixresin and its energy is absorbed and diverted.

Furthermore, the acrylic impact modifier has advantages in that it maybe produced without degradation of the transparency by designing therubber and matrix layers so that the refractive indexes are equal.However, when the outer stress is applied to the product, the coloraround the stressed portion changes to white.

To prevent such problem, the Japanese Patent Publications 1980-148729,1971-31462 and 1979-1584 proposes the process including the stages ofemulsion polymerization for making the impact modifier have a core-shellstructure and finally polymerizing a hard polymer having good mixingability with the matrix resin to the outer layer. However, such processincludes problems in that the amount of impact modifier should beincreased because of less content of rubber therein and the thickness ofthe outer layer is limited because the impact strength is more weakenwhen the outer layer thickness is increased.

The Japanese Patent Publication 1981-96862 discloses the process usinggraft copolymers having an increased content of rubber component byhighly crosslinking the rubber polymer. However, such a highlycrosslinked polymer has a degraded impact absorbing effect due to itsdecreased rubber resilience and a degraded mixing property with thematrix thereby decreasing the processibility of the product.

Furthermore, when forming the impact modified PMMA sheet by using theabove mentioned impact modifier according to the prior arts, manyproblems have arisen in that the process is complicated and productivityis decreased because the PMMA and impact modifier should be made byseparate processes and be supplied to an extruders, separately.

The formed sheet product has a degraded transparency because the impactmodifier is not uniformly dispersed therein. Therefore, the thickness ofthe sheet product is limited in obtaining the necessary transparency.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a PMMA resin with animpact modifier capsulated therein having good transparency and goodimpact resistance properties.

It is another object of the present invention to provide a process formanufacturing a PMMA resin with an impact modifier capsulated thereinwhich has advantages that the process using in producing the product issimplified and the productivity is increased.

To achieve the above objects, the present invention provides a PMMAresin with an impact modifier capsulated therein which comprises a coreof a glass polymer, an intermediate layer of a rubber copolymer graftedto the core and an outer layer of a glass polymer grafted to theintermediate layer. The products have a granular shape, with the amountof the core being between 5 to 20 weight %, the amount of theintermediate layer being between 10 to 70 weight % and the outer layerbeing 25 to 85 weight %, the intermediate of the rubber copolymer beinga copolymer of at least one monomer selected from butylacrylate orbutadiene and at least one monomer selected from styrene or styrenederivative, the outer layer of the glass polymer containing a chaintransfer agent.

The PMMA resin with the impact modifier capsulated therein according tothe present invention has in three layer structure an impact modifier ofa glass polymer core and an intermediate layer of a rubber copolymergrafted to the core and an outer layer of a glass polymer(as a matrixresin) grafted to the intermediate.

Preferably, in the PMMA resin with the impact modifier capsulatedtherein according to the present invention, the weight % or averagediameter of the outer layer is higher or larger than that of the core.As the result, when preparing transparent sheet or molding a products,there is no need to use the matrix PMMA resin thereby simplifying themolding process and increasing the productivity.

The PMMA resin with the impact modifier capsulated therein according tothe present invention is characterized by including a chain transferagent in the outer layer. The chain transfer agent acts to adjust themolecular weight and melt viscosity of the outer layer withoutdecreasing an impact resistance thereof.

Furthermore, the PMMA resin with the impact modifier capsulated thereinaccording to the present invention is characterized in that theintermediate layer of a rubber polymer is composed of the copolymer ofat least one monomer selected from butylacrylate or butadiene and atleast one monomer selected from the styrene or styrene derivatives.

According to the present invention, a process for producing a PMMA resinwith the impact modifier capsulated therein which includes threeemulsion polymerizing stages as following:

First emulsion polymerizing stage for preparing emulsion of a glasspolymer for a core with the conversion rate of 93 to 99%, which has anaverage diameter of 30 to 200 nm, by inputting the composition solutionof a part of the first monomers, deionized water, emulsifier, graftingagent, and crosslinker under the nitrogen atmosphere into a reactor,heating and agitating the composition solution, emulsion-polymerizingthe composition by dropping a polymerization initiator when thetemperature of the composition reaches 50 to 90° C., continuouslypolymerizing the composition dropping the remaining first monomers whenseed emulsions are formed, and finally inputting the initiator into thecomposition at the end of the polymerization;

Secondary emulsion-polymerizing stage for producing the polymer emulsiongrafted to the glass polymer core with the conversion rate of 93-99% andthe average.thickness of 10 to 150 nm, by agitating the emulsion at thetemperature of 50 to 90° C. dropping an emulsifier, initiator, acrosslinker, the second monomers of at least one of butylacrylate orbutadiene and at least one of styrene or styrene derivatives, andinputting the additional initiator at the end of the polymerization;

Third emulsion-polymerization stage for producing a PMMA resin with animpact modifier capsulated therein with the conversion rate of more than93%, in which an glass polymer (outer layer) is grafted to the rubberpolymer (intermediate layer) with the thickness of 60 to 3000 nm, bycontinuously polymerizing dropping the third monomers and polymerizationinitiator and inputting a chain transfer agent and polymerizationinitiator at the end of the polymerization.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

At first, the process for emulsion-polymerization the first monomer isdisclosed in detail below.

The composition solution of a part of the first monomers, deionizedwater, emulsifier, grafting agent, and crosslinker is inputted into areactor under the nitrogen environment, the composition solution isheated and agitated. When the temperature of the composition reaches 50to 90° C., the composition is emulsion-polymerized adding apolymerization initiator thereto. Finally, the polymerization initiatoris added to the composition at the end of the polymerizing stage. Thus,the emulsion of a glass polymer for a core is obtained.

In the first emulsion polymerizing stage, the average diameter of theemulsion of a glass polymer for a core is dependent on the amount of theused emulsifier and the first monomer. Less amount of the first monomermakes the size of the glass polymer to be decreased thereby forming morerubber polymer in the impact modifier. The first monomer is preferablyused in the amount of 5 to 20 weight part to the total amount of theused monomers. Furthermore, it is preferred to control the averagediameter in the range between 30 and 200 nm by controlling the amount ofthe emulsifier.

It is also preferred to emulsion-polymerize the first monomer so thatthe ratio of converting the first monomer to the glass polymer is93-99%. If the conversion ratio is less than 93%, the thermal stabilityis lowered thereby causing its decomposition in the processing.

The first monomer used in the first stage may be at least one monomerselected from the group of the aromatic vinyl-monomer, (meta)acrylicalkylester having 1˜20 carbon atoms, (meta)acrylalkyl arylester having1˜20 carbon atoms and (meta)acrylic fluoralkylester having 1˜20 carbonatoms.

The deionized water is obtained from the ion exchanger and having theelectric resistance of over 1 MΩ under the nitrogen atmosphere. Thedeionized water is used in the amount of 80 to 800 weight part of thefirst monomer.

The secondary emulsion-polymerizing stage is described in detail below.

The glass polymer emulsion obtained from the first stage is agitated andpolymerized at the temperature of 50 to 90° C. dropping emulsifier,initiator, grafting agent, crosslinker and the secondary monomer andadding the polymerization initiator at the end of the polymerizing. Therubber polymer of the intermediate layer is grafted to the glass polymerof the core by the emulsion-polymerization. The impact resistance isimproved with the more rubber polymer in the impact modifier.

In the secondary stage, it is important to use the rubber polymer of 10to 70 weight part to the total amount of the used monomers. If therubber polymer less 10 weight part is provided in the impact modifier,the impact resistance is decreased. The average thickness of thecrosslinked rubber polymer is between 10 and 150 nm, more preferablybetween 30 and 80 nm.

It is preferred to emulsion-polymerize the secondary-monomer so that theconversion ratio of the secondary monomer converted into the rubberpolymer in the secondary stage is between 93 and 99%. If the conversionratio is less than 93%, the thermal stability is reduced thereby causingits decomposition in the processing.

In the secondary stage, the monomers may be clustered when the droppingtime of the secondary monomer and polymerizing time are not proper orthe surfactant is not used.

At least one of butylacrylate or butadiene and at least one of styreneor styrene derivatives are used as the secondary monomer. The styrenederivative substituted with a halogen, or substituted with a alkylradical or a aryl radical having 1 to 20 carbon atoms.

The third emulsion-polymerizing stage is described in detail below.

The emulsion produced from the secondary emulsion-polymerizing stage iscontinuously polymerized dropping the third monomer as a matrixcomponent and the polymerization initiator thereto and adding a chaintransfer agent and polymerization initiator at the end of thepolymerizing so that the glass polymer (outer layer) grafted to therubber polymer (intermediate layer) is obtained.

In the third emulsion-polymerizing stage, it is important feature of thepresent invention that the chain transfer agent is added to control themolecular weight. The chain transfer agent may be at least one selectedfrom the group including sulfur compounds such as n-butylmercaptanhaving 1 to 20 carbon atoms and n-butyl(di) sulfide, amino compoundssuch as butylamine and triethyl(methyl) amine, halogen compounds such aschloroform and tetrachloro(bromo) methane, alcohol group includingethanol or acetone. The chain transfer agent is preferably used at theratio of 0.02 to 5.0 weight part to 100 weight part of the thirdmonomer.

It is important that the amount of the third monomer is 25 to 85 weightpart to the amount of total monomers. If the third monomer is less than25 weight part, additional PMMA resin should be used therebycomplicating the producing process and decreasing the productivity. Thethird monomers is at least one selected from group including aromaticvinyl group monomer, (meta)acrylic alkylester having 1˜20 carbon atoms,(meta)acrylic alkylarylester having 1˜20 carbon atoms and (meta)acrylicfluoralkylester having 1˜20 carbon atoms.

It is desirable to control the average thickness of the grafted thirdmonomer 60 to 3000 nm, more preferably 80 to 200 nm. In the third stageis preferred to polymerize the third monomer with the conversion ratioof more than 95%. If the conversion rate is less than 95%, the thermalstability and physical properties are degraded thereby causing itsdecomposition in the processing.

The emulsifier(surfactant) may comprises the anionic emulsifier ofpotassium salt, ammonium and sodium of alkylsulfate with 4 to 30 carbonatoms, the reactive emulsifier of the same functional group oramphoteric emulsifier. More particularly, the emulsifier may be the oneselected from the sodium dodecylsulfate, sodium dioctyl-sulfosuccinateor sodium dodecylbenzenesulfate. Preferably, the emulsifier iswater-soluble material for increasing the stability of the polymer. The0.2 to 4 weight part of emulsifier is used to the total monomers.

The crosslinker may comprises 1,2-ethanedioldi(meta)acrylate,1,3-propanedioldi(meta)acrylate, 1,3- or 1,4-butanedioldi(meta)acrylate,divin-ylbenzene, ethyleneglycoldi(meta)acrylate,propyleneglycoldi(meta)acrylate, butyleneglycoldi(meta)acrylate,triethyleneglycoldi(meta)acrylate, polyethyleneglycoldi(meta)acrylate,polypropyleneglycoldi(meta)acrylate, polybutyleneglycoldi(meta)acrylateor allyl(meta)acrylate.

Preferably, the amount of crosslinker used is 0.1 to 15 weight part tothe total monomers.

The polymerization initiator may be comprises cumenehydroperoxidpotassium persulfate or sodium persulfate azo group water-solubleinitiator.

Preferably, the amount of initiator used is 0.02 to 2.0 weight part tothe total monomers.

When the three stages of process is finished, the emulsion having thestructure of three layers is obtained.

The granular emulsion is subsequently dropped in the agitated solutionof 0.1 to 2 weight % magnesium sulfate or potassium chloride preheatedat 50 to 100° C. thereby obtaining granules precipitated in theemulsion.

For obtaining finally the PMMA resin with an impact modifier capsulatedtherein according the present invention, the precipitated granules arewashed several times with the distilled water of about 70° C. and aredried in the oven at 80° C. The precipitated granules can be also driedby a spray drier.

The produced PMMA with an impact modifier capsulated therein comprises acore made of the glass polymer of the first monomer, an intermediatelayer of a rubber copolymer grafted to the core and an outer layer of aglass polymer grafted to the intermediate layer, the resin having agranular shape, the acryl resin having in the ratio of the 5 to 20% ofthe core : 10 to 70 weight % of the intermediate layer : 25 to 85 weight% of the outer layer, and the thickness in the ratio of 30 to 200 nm ofthe core : 10 to 150 nm of the intermediate layer : 60 to 3000 nm of theouter layer.

Furthermore, the outer layer of the glass polymer contains a chaintransfer agent and the intermediate layer is consisted of the copolymerof at least one monomer selected from butylacrylate or butadiene and atleast one monomer selected from styrene or styrene derivatives.

The PMMA resin with an impact modifier capsulated therein according tothe present invention has the properties of good impact resistance andof good transparency due to its excellent dispersive properties in caseof molding the thick sheet. Furthermore, the powdered PMMA resin alsohas the improved physical properties due to excellent porcessibility.

As the resin of the present invention has a structure that matrix resinis grafted to the glass polymer(core), the stage of compounding thematrix resin and the impact modifier can be omitted. As result thepelletizing process is simplified and the productivity is increased. ThePMMA resin with an impact modifier capsulated therein according to thepresent invention is the one that integrated with the impact modifierand the matrix resin.

According to the present invention, the physical properties are testedas following:

ASTM D-1003 Method for the transparency(%) test; ASTM D-256 Method forthe impact strength(kg.cm/cm) test; ASTM D-790 Method for the bendingstrength(kg/cm²) test; and ASTM D-790 Method for the elasticdeformation(kg/cm²) test.

EXAMPLE 1

The deionized water 700 g is heated at 70° C. in the reactor having thevolume of 3 litters under the nitrogen atmosphere and the composition 20g composed of the methylmethacrylate 85 g, ethylmethacrylate 10 g,allylmethacrylate 0.45 g and sodium dioctylsulfosuccinate 0.78 g isadded and agitated for 15 minutes. The 1% potassiumpersulfate solution 8ml is further added to the reactor and the composition is agitated for60 minutes. The residual composition is dropped at the rate of 5g/minute into the reactor when the polymerization process is almostcompleted. After the dropping step, the polymerization is furtherperformed to obtain the glass polymer as the core having the averagediameter 180 nm, of which the conversion ratio is 94%.

The glass polymer is agitated for 15 minutes adding the 1% potassiumpersulfate solution 13 ml and the composition solution composed ofbutylacrylate 142 g, styrene 23.3 g, allylmethacrylate 1.6 g and sodiumdioctylsulfosuccinate 1.3 g is dropped into the reactor at the rate of 8g/minute. After the dropping step, the composition is polymerized for240 minutes and further polymerized for 15 minutes adding thepotassiumpersulfate solution 6 ml to obtain the emulsion that thecrosslinked rubber polymer is grafted to the core with the 96% ofconversion ratio. The average thickness of the intermediate layer isabout 80 nm.

The obtained granular emulsion is further polymerized in the reactor for100 minutes dropping the solution of the methylmethacrylate 333 g andethylacrylate 17.0 g at the rate of 3 g/minutes. The potassiumpersulfatesolution 8 ml and chloroform 7 g as the chain transfer agent are furtheradded thereto when the polymerization process is almost completed, andthe polymerization is finished to obtain the emulsion that the glasspolymer as an outer layer is grafted to the intermediate layer. Theaverage thickness of the grafted outer layer is about 100 nm.

The obtained emulsion is agitated with dropping the 1% magnesiumsulfatesolution preheated at 80° C. to obtain the precipitates. The precipitateis washed three times with the distilled water of 70° C., and dried inthe vacuum oven at 60° C. for 2 days to obtain the PMMA resin with animpact modifier capsulated therein. The impact modified PMMA resin hasthe ratio by weight of the core, intermediate layer and outer layer of96:160:350.

The mixture of the PMMA resin with an impact modifier capsulated therein4000 g and the additives of Tinuvin-312 8 g, Irganox B-900 4g, Uvitex OB0.04 g and Blue-pigment 0.008 g is extruded to form the impact testspecimens with the thickness of 4 mm for test of physical properties asshown in Table 2.

Example 2 and Comparative Examples 1 and 2

The PMMA resin with an impact modifier capsulated therein and testspecimens are prepared by the same process and conditions as the Example1 except that the ratio of the thickness and weight of the core,intermediate layer and outer layer in the three stages and the amount ofthe chain transfer agent added in the emulsion polymerization arechanged as in Table 1.

Comparative Example 3

The deionized water 700 g is heated at 70° C. in the reactor having thevolume of 3 L under the nitrogen atmosphere and the composition solution40 g composed of the methylmethacrylate 190 g, ethylmethacrylate 20 g,allylmethacrylate 0.9 g and sodium dioctylsulfosuccinate 1.45 g is addedand agitated for 15 minutes. The 1% potassiumpersulfate solution 15 mlis further added to the reactor and the composition is agitated for 60minutes. After the dropping step, the polymerization is furtherperformed to obtain the glass polymer as the core having the averagediameter 180 nm, of which the conversion ratio is 94%.

After the 1% potassiumpersulfate solution 25 ml is further added to thereactor and is agitated for 15 minutes, the composition solution of thebutylacrylate 284 g, styrene 40 g, allylmethacrylate 6.5 g and sodiumdioctylsulfosuccinate 2.5 g is added at the rate of 8 g/minute into thereactor. The emulsion polymerization is further proceeded for 240minutes and the emulsion is agitated for 15 minutes adding the 1%potassiumpersulfate solution 12 ml to obtain the emulsion that therubber polymer is grafted to the core with the 96% of conversion ratio.The average thickness of the intermediate layer is about 70 nm.

The above emulsion is further polymerized for 100 minutes dropping thecomposition solution at the rate of 3 g/minute which is composed ofmethylmethacrylate 86 g and ethylacrylate 4.5 g to obtain the granuleemulsion that the glass polymer as an outer layer is grafted to theintermediate layer. The average thickness of the grafted outer layer isabout 48 nm.

The obtained emulsion is agitated with dropping the 1% magnesiumsulfatesolution preheated at 80° C. to obtain the precipitate. The emulsionpowder is washed three times with the distilled water of 70° C. anddried in the vacuum oven at 60° C. for 2 days to obtain the PMMA resinwith an impact modifier capsulated therein.

The mixture of the PMMA resin 3090 g with an impact modifier 908 g andthe additives of Tinuvin-312 8 g, Irganox B-900 4 g, Uvitex OB 0.04 g isextruded to form the impact test specimens with the thickness of 4 mmfor test of physical properties as shown in Table 2.

TABLE 1 Emulsion Polymerization Conditions Core:Intermediate layer:OuterAmount of Added Chain layer transfer Weight Thickness agent(Chloroform)Example 1 16:26:58 180:80:100 7 Example 2 10:24:66 180:120:500 8Comparative  3:77:20  60:200:40 7 Example 1 Comparative 45:18:37270:8:620 8 Example 2 Comparative 33:53:14 180:70:48 0 Example 3

TABLE 2 Results of Pysical Properties Test Elastic Produc- ImpactBending defor- Trans- tivity strength strength mation parency (cost (kg· cm/cm) (kg/cm²) (kg/cm²) (%) down. %) Example 1 6.5 750 19000 92 15Example 2 5.8 820 20000 91 13 Comparative Example 1 6.0 900 22100 88 0Comparative 3.2 830 18700 84 0 Example 2 Comparative 4.5 720 18500 85 −2Example 3

The PMMA resin with an impact modifier capsulated therein according tothe present invention has the property of good dispersion of the impactmodifier in the processing because the much PMMA resin(outer layer) andimpact modifier(i.e., core and intermediate layer) are integrated ineach particle.

Therefore, the produced resin has the good impact resistance andtransparency without degradation of the transparency in case of thethick sheet product.

Since the PMMA resin with an impact modifier capsulated thereinaccording to the invention can be used to produce sheets and othermolding articles by a single screw extruder whereby the apparatus issimplified and the productivity is increased compared to a twin screwextruder.

While this invention has been described in connection with what ispresently considered to be the most practical and preferred embodimentsand examples, it is to understood that the invention is not limited tothe disclosed embodiment, but, on the contrary is intended to covervarious modifications and equivalent arrangements and methods includedwithin the spirit and scope of the appended claims.

What is claimed is:
 1. A PMMA resin containing an impact modifiercapsulated therein, said impact modifier comprising a core of a glasspolymer, an intermediate layer of a rubber copolymer grafted to the coreand an outer layer of a glass polymer grafted to the intermediate layer,the impact modified PMMA resin having a granular shape, the amount ofthe core being 5 to 20 weight %, the amount of the intermediate layerbeing 10 to 70 weight % and the amount of the outer layer being 25 to 85weight %, the intermediate of the rubber copolymer being a copolymer ofat least one monomer selected from the group consisting of butylacrylateand butadiene and a monomer of styrene, the outer layer of a glasspolymer containing a chain transfer agent.
 2. The PMMA resin containingan impact modifier capsulated therein as defined in claim 1, wherein theratio of the thickness of the core, intermediate layer and outer layeris 100 to 200 nm:10 to 150 nm 60 to 3000 nm.
 3. The PMMA resincontaining an impact modifier capsulated therein as defined in claim 1,wherein the core and outer layer are the homopolymer or copolymers of atleast one monomer selected from the group consisting of an aromaticvinyl monomer, a (meta)acrylic alkylester having 1˜20 carbon atoms, a(meta)acrylic alkylarylester having 1˜20 carbon atoms and a(meta)acrylic fluoralkylester having 1˜20 carbon atoms.
 4. The PMMAresin containing an impact modifier capsulated therein as defined inclaim 1, wherein chain transfer agent is at least one member selectedfrom the group consisting of sulfur compounds, amino compounds, alcoholand acetone.
 5. The PMMA resin containing an impact modifier capsulatedtherein as defined in claim 1, wherein styrene which is a monomer forthe copolymers of the intermediate layer is a compound substituted witha halogen, or substituted with an alkyl radical or an aryl radicalhaving 1-20 carbon atoms, respectively.
 6. A process for producing aPMMA resin with an impact modifier capsulated therein which comprisesthe following three emulsion polymerizing stages: Conducting a firstemulsion polymerizing stage for preparing a granular emulsion of a glasspolymer for a core with a conversion ratio of 93-99% and an averagediameter of 80-200 nm, by adding the composition of a part of the firstmonomers, deionized water, an emulsifier, a grafting agent, and acrosslinking agent under a nitrogen atmosphere, into a reactor, heatingand agitating the composition, emulsion-polymerizing the compositionadding a polymerization initiator thereto when the temperature of thecomposition reaches 50-90° C., continuously polymerizing the compositionwhile adding the remaining first monomer to form a seed emulsion, andfinally inputting the initiator into the composition at the end of thepolymerizing step, Conducting a secondary emulsion polymerizing stagefor producing the polymer emulsion grafted to the glass polymer granulecore a the conversion ratio of 93˜99% and an average thickness of 10-150nm, by agitating the emulsion at a temperature of 50-90° C., adding anemulsifier, a crosslinking agent, and the secondary monomers of at leastone of butylacrylate or butadiene and styrene, and inputting thepolymerization initiator at the end of the polymerizing; Conducting athird emulsion polymerizing stage for producing a PMMA resin with animpact modifier capsulated therein with a conversion ratio is of morethan 95%, in which a glass polymer (outer layer) is grafted to therubber polymer (intermediate layer) with the thickness of 60˜3000 nm, bycontinuously polymerizing and adding the third monomers andpolymerization initiator, and adding a chain transfer agent andpolymerization initiator at the end of the polymerization.
 7. Theprocess for producing a PMMA resin with an impact modifier capsulatedtherein as defined in claim 6, wherein the chain transfer agent is atleast one member selected from the group consisting of sulfur compounds,amino compounds, alcohol and acetone.
 8. The process for producing aPMMA resin with an impact modifier capsulated therein as defined inclaim 6, wherein the ratio of the content of the first monomer, thesecond monomer and the third monomer is 5 to 20 part:10 to 70 part:25 to85 part to 100 weight part of the total monomers.
 9. The process forproducing a PMMA resin with an impact modifier capsulated therein asdefined in claim 6, wherein the first and third monomers is at least onemonomer selected from the group consisting of an aromatic vinyl monomer,a (meta)acrylic alkylester having 1˜20 carbon atoms, a (meta)acrylicalkylarylester having 1˜20 carbon atoms and a (meta)acrylicfluoralkylester having 1˜20 carbon atoms.
 10. The process for producinga PMMA resin with an impact modifier capsulated therein as defined inclaim 6, wherein the polymerization initiator is cumenehydroperoxide,potassiumpersulfate or a sodiumpersulfate azo group water-solubleinitiator.
 11. The process for producing a PMMA resin with an impactmodifier capsulated therein as defined in claim 6, wherein theemulsifier is a potassium salt, or an ammonium or sodium of alkylsulfatehaving 4-30 carbon atoms.
 12. The process for producing a PMMA resinwith an impact modifier capsulated therein as defined in claim 6,wherein the chain transfer agent content is 0.02 to 4.0 part to 100parts of the third monomer.
 13. The process for producing a PMMA resinwith an impact modifier capsulated therein as defined in claim 6,wherein the deionized water has an electric resistance of more than 1 MΩmeasured under a nitrogen atmosphere.
 14. The process for producing aPMMA resin with an impact modifier capsulated therein as defined inclaim 6, wherein the styrene which is a monomer for copolymers of theintermediate layer is a compound substituted with a halogen, orsubstituted with an alkyl radical or an aryl radical having 1-20 carbonatoms.